In recent years, with energy density of battery cells becoming higher, it is increasingly urgent for electric vehicles to improve safety of batteries, and thermal runaway is a key issue in safety research on battery cells. As a power source for an electric vehicle, a battery pack is generally disposed in a chassis of the electric vehicle. A battery pack includes a plurality of battery modules, and each battery module has a plurality of battery cells arranged in rows and a plurality of bus bars electrically connected to the plurality of battery cells. In the existing technologies, a vent of a battery cell faces upward, that is, the vent directly faces a passenger above the battery pack. As a result, thermal runaway would directly threaten a passenger's safety due to upward energy release and flames by the battery cell.